Ok, so I'm making use of the DRW for assemblies as a production card for the shop here in the company.
My assembly consists of the final product and includes everything necessary.

In my DRW, I have one BOM (part list with no sub assemblies) which consists of "Item No.", "Part Number/Name", "Description", "Quantity" and a couple other custom columns.
This quantity, automatically generated by solidworks is auto-linked by whatever quantity the assembly consists of.
Now, for production purposes, I also indicate the quantity needed for that final product (which in the drawing is simply a "NOTE" linking back to a custom property in my main assembly).

My question here, is how to create an equation, that for every row in one column will tell me the TOTAL quantity of parts needed for "n" main assemblies.
So, if my custom property "QUANTITY" reads 3 and I have 2 instances of the part "OuterTank.sldprt" in my main assembly, I would like this custom column in my BOM to read "6", where the formula/equation would be something like {partQTY} * {MainAssemblyCSTMPRPqty}.


Note: I understand this may not be the best practice, but for my purposes, it is exactly what I need, I would really appreciate some ideas on this and even more the solution.

I hope I made sense, and was clear enough.
Sorry for my poor grammar.

Regards